1. Field of the Invention
The present invention relates to an aqueous dispersion composition for chemical mechanical polishing (hereunder referred to as “aqueous dispersion”) that is useful in the manufacture of semiconductor devices. More specifically, the invention relates to an aqueous dispersion prepared by dispersing in water polymer particles having functional groups that can react with the metals of polishing surfaces (particularly functional groups that can form cations), which is suitable for polishing of working films and the like in semiconductor devices.
2. Description of the Prior Art
Improved integration and increased multilayer wiring of semiconductor devices have led to introduction of a certain type of chemical mechanical polishing (hereunder referred to as “CMP”) technique for polishing of working films and the like. This is a process whereby a wiring material such as tungsten, aluminum, copper or the like is embedded in a hole or groove formed in an insulator film on a processing wafer and then polishing is performed to remove the excess wiring material to thereby form the wiring. In this polishing technique, aqueous dispersions containing abrasive particles made of silica or metal oxides have conventionally been used as polishing materials. However, the abrasive particles have high hardness and have therefore presented the problem of creating scratches and dishing on polishing wafer surfaces, thus lowering the reliability of the LSI. A particularly emphasized area of research is focused on control of scratches and the like in porous insulator films with low hardness that are currently being studied for use.
In order to inhibit creation of scratches and the like, the use of polymer particles as abrasive particles has been proposed. Japanese Laid-open Patent Publication No. 270400 of 1998 describes a polishing material for manufacture of semiconductor devices that comprises an aqueous emulsion containing vinyl compound polymer particles obtainable by emulsion polymerization. Here, 2,2-azobis(2-aminopropane) hydrochloride is mentioned as an example of the polymerization initiator for emulsion polymerization. This compound, however, is only given as an example of a polymerization initiator, and there is no mention whatsoever regarding whether it has any other effects. Also, Japanese Laid-open Patent Publication No. 168431 of 1998 discloses a polishing slurry containing abrasive particles coated with a polyelectrolyte. However, the abrasive particles are inorganic particles. Moreover, it is also suggested that the polishing rate is reduced when the particles are totally covered with the polyelectrolyte.